In some facilities, the appropriate rig is not available and tools cannot be run-in on rigid or coiled tubing. In those instances, the downhole tools are connected to a running tool which is, in turn, supported by one type or another of a line. One common form is a wireline; however, other types of line supports are intended to be encompassed in the term "line" or "wireline" as used in this application. One of the problems in the past with running in tools on wireline has been that if an obstruction of sorts is encountered prior to reaching the desired depth, the running tools of the prior art would release. In some designs, if the downhole tool becomes supported, allowing the wireline to go slack and the wireline is subsequently tensioned, the running tool releases from the downhole tool. One variation in a wireline-supported running tool, that has been developed by Halliburton in its Modular Gun System, involves up and down movement on the wireline to set a gun hanger, followed by a decrease in wireline weight at the surface to verify that such a hanger had been set. When thereafter additional weight was slacked off, oil metered through an orifice flowed in the hydraulic running tool. After delay of some 5 minutes, the tool automatically released from the gun hanger. While this design allowed surface personnel to react to avoid an inadvertent release due to the time delay provided by metering the oil flow through a restriction orifice, a better design was needed to ensure that the tool being conveyed will not release from the running tool until it is properly positioned at the appropriate depth. Another requirement was to allow the running tool to automatically reset so that it could be reused for multiple-trip operations without having to be disassembled and redressed. This type of an issue is common in designs that break shear pins to allow a release mechanism to operate.
Some systems have been tried which incorporated a rupture disk which, in order to release, involved an increase in wellbore pressure to break the rupture disk. This, in turn, created an unbalanced force which broke a shear pin on a release piston, which in turn pulled locking collets off of their support. These designs were good for a single use and had to be disassembled to be redressed to replace the shear pins. An example of this design is the model GRD Running Tool, product No. 493-46 made by Baker Oil Tools.
Various tubing-conveyed fishing tools have been used which apply a force generated by fluid flow through an orifice for release. These tools would automatically reset after the hydraulic pressure was removed from the tubing. Typical examples of such tools are U.S. Pat. Nos. 5,242,201 and 5,581,014. However, these tools were not configured to operate on wireline. Yet other tools using wireline worked on the jarring concept. A Model W Running Tool from Baker Oil Tools required upward jarring to release the downhole tool. The Model M Running and Pulling Tool made by Baker Oil Tools required jarring down to shear a shear pin to remove support for dogs which held the downhole tool so that a release could occur. The soft release running tool, product No. 811-40 by Baker Oil Tools, released by an upward pull followed by a slacking off. Also of general interest in this area are U.S. Pat. Nos. 4,361,188 and 5,180,015.
The shortcoming of the prior art tools was that for a wireline application, they would not give assurance of premature release should the downhole tool become supported in a location above the desired depth. Additionally, these tools did not facilitate many trips in succession because they had to be redressed after each release due to their use of a shear pin or pins in the release mechanisms. Yet other designs in the prior art which provided the automatic resetting feature and released with hydraulic pressure required the running tool or fishing tool to be run-in the wellbore on rigid or coiled tubing. Accordingly, one of the objectives of the present invention is, in applications where equipment is not available to run rigid or coiled tubing, to have a running tool supported on a wireline which can give assurance that it will not prematurely drop the downhole tool, while at the same time providing features of automatic resetting, coupled with simple and safe operation. These objectives will be more readily understood by those skilled in the art from a review of the preferred embodiment described below.